1. Field of the Invention
The present invention relates to the field of microscopy, and in particular to an aid for a microscope user.
2. Description of the Related Art
Microscopes are commonly used to view images of very small objects. A typical optical microscope has several objective lenses, of different magnifying power, to enable an object on a microscope slide to be viewed at different magnifications.
A problem with viewing an object through a microscope is that only a portion of the object can be seen in the field of view at any one time. The higher the magnifying power of the objective lens, the smaller the area of the object visible in the field of view. Thus, at very high magnifications (e.g. use of a 20× (or above) objective lens), the field of view only contains a very small part of the complete object. Consequently, characteristic features of the object, such as its outline shape, or the distinctive shape of features within the object, are unlikely to be visible in the field of view, or, if visible are unlikely to be of a size sufficient to enable determination of the position of the visible area within the overall object.
When using a microscope for studying a biological specimen, for example, a user will typically look at the specimen on the microscope slide with the naked eye (e.g. by holding the slide up to the light) to get a sense of the outline shape of the specimen and the location of distinctive visible features within the outline. The user may then view the object through the microscope at low magnification to more clearly identify the main distinctive features of the object before viewing the object in detail at high magnification.
When viewing the specimen at high magnification, the user estimates the position of the portion of the specimen in the field of view within the overall specimen based on his or her memory of the shape of the specimen. As a result, even the most experienced microscope users find it difficult to determine the exact position of a part of the specimen contained within a field of view in relation to the overall specimen, especially at high magnifications.
Recently, developments have been made in the field of “virtual microscopy” in which digital images of an object are captured from a microscope by a digital camera and assembled together by image processing software to form an overall image of the object which can be displayed on a display screen. An example of a virtual microscopy technique is described in EP-A-0 994 433 in the name of Fairfield Imaging Limited. In the described technique, adjacent images are captured from a microscope at high magnification/resolution and are assembled together to provide a composite image. A low magnification/resolution copy of the image is obtained by image processing which is displayed on a display screen and used as a “navigation map”. A user can select, from the navigation map, a portion of the low magnification/resolution image for viewing at high resolution. Thus, the user of a virtual microscope has the benefit of knowing the positional relationship of a displayed high magnification image relative to the overall object.
Although virtual microscopy is increasingly used, it necessitates the provision of an expensive, high precision microscope that is dedicated to imaging microscope slides, along with associated equipment including a stage driver, high quality digital or video camera and associated workstation. Such additional equipment can be bulky, and can inhibit normal use of the microscope when not performing imaging for virtual microscopy.
It would be desirable to provide a system and method which can be used with a conventional microscope that provides some of the aforementioned advantages of virtual microscopy. In particular, it would be desirable to provide a method and apparatus that gives an indication of the position of an area of a microscope specimen, contained within the field of view of a microscope, within the complete specimen.
One method for determining the position of an area of a microscope specimen contained within the field of view of a microscope within the complete specimen is to use an expensive robotic microscope stage which has a stage driver and sensors in order to determine the position of the field of view using the stage coordinates. However this technique is complex and requires expensive equipment not readily available to an average microscope user.
The present invention therefore further aims to obviate the need for such expensive equipment when determining the positional information.